Minimal left-right symmetric intersecting D-brane model

TL;DR

This paper explores a minimal left-right symmetric extension of the standard model using intersecting D-branes, analyzing its phenomenology and constraints from LHC data, and finds that W' bosons with masses above 3.5 TeV are still viable.

Contribution

It introduces a novel D-brane based left-right symmetric model with specific symmetry breaking mechanisms and analyzes its experimental constraints from LHC data.

Findings

W' bosons with masses above 3.5 TeV are not excluded by current LHC data.

The model predicts comparable branching ratios of W' into dilepton and dijet channels.

The model's gauge symmetry breaking suppresses Majorana neutrino masses.

Abstract

We investigate left-right symmetric extensions of the standard model based on open strings ending on D-branes, with gauge bosons due to strings attached to stacks of D-branes and chiral matter due to strings stretching between intersecting D-branes. The left-handed and right-handed fermions transform as doublets under Sp(1)_L and Sp(1)_R, and so their masses must be generated by the introduction of Higgs fields in a bi-fundamental (2,2) representation under the two Sp(1) gauge groups. For such D-brane configurations the left-right symmetry must be broken by Higgs fields in the doublet representation of Sp(1)_R and therefore Majorana mass terms are suppressed by some higher physics scale. The left-handed and right-handed neutrinos pair up to form Dirac fermions which control the decay widths of the right-handed W' boson to yield comparable branching fractions into dilepton and dijets channels. Using the most recent searches at LHC13 Run II with 2016 data we constrain the (g_R, m_{W'}) parameter space. Our analysis indicates that independent of the coupling strength g_R, gauge bosons with masses m_{W'} \agt 3.5~{\rm TeV} are not ruled out. As the LHC is just beginning to probe the TeV-scale, significant room for W' discovery remains.